The Study
The Nurse's Health Study is following the lives and health of 121,701 registered nurses enrolled in 1976. The findings are published in the Archives of Internal Medicine. The nurses are surveyed every two years in this prospective study, which includes both pre-menopausal and post-menopausal women. The size of the survey and the fact that it is following women throughout their lives contributes to the integrity of its results.
How much walking and how vigorous?
The definition of brisk walking in the survey was walking 3 - 3.9 miles per hour. Walking faster was rated as very brisk. These were counted as "vigorous" physical activities. Walking at 3 to 3.9 miles per hour for most people is a rate where you may be breathing hard but would not be out of breath.
Time spent in vigorous physical activity was surveyed. The results showed fewer breast cancer diagnoses in those who engaged in vigorous physical activity for 7 hours a week or more.
The control group, by comparison, were those women who spent less than 1 hour a week in vigorous physical activity.
Other vigorous physical activities listed were jogging, running, bicycling, swimming, tennis and/or squash, calisthenics, aerobics, and use of a rowing machine.
Is it too late to start now?
That question has yet to be answered by the research. Some theorize that physical activity reduces your exposure to certain ovarian hormones and thus prevents breast cancer. Less exposure over many years may be important, meaning that you should be exercising vigorously at all ages. Or, less exposure at the present time may keep it from developing now. Don't wait to find out! Exercise has many benefits for preventing heart disease and stroke as well.
The Risks
A woman's chance of developing breast cancer in her lifetime is 1 in 8, with 185,000 new diagnoses each year in the US (1% of these are in men) and over 44,000 deaths each year. It is the most common cancer in women.
Links
Health Benefits of Walking
Breast Cancer About.com
Breast Cancer Articles from your About Guide to Women's Health
Cancer from your About Guide to Cancer
